#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import struct
from struct import unpack

from ambari_ws4py.utf8validator import Utf8Validator
from ambari_ws4py.messaging import (
  TextMessage,
  BinaryMessage,
  CloseControlMessage,
  PingControlMessage,
  PongControlMessage,
)
from ambari_ws4py.framing import (
  Frame,
  OPCODE_CONTINUATION,
  OPCODE_TEXT,
  OPCODE_BINARY,
  OPCODE_CLOSE,
  OPCODE_PING,
  OPCODE_PONG,
)
from ambari_ws4py.exc import (
  FrameTooLargeException,
  ProtocolException,
  InvalidBytesError,
  TextFrameEncodingException,
  UnsupportedFrameTypeException,
  StreamClosed,
)
from ambari_ws4py.compat import py3k

VALID_CLOSING_CODES = [1000, 1001, 1002, 1003, 1007, 1008, 1009, 1010, 1011]


class Stream(object):
  def __init__(self, always_mask=False, expect_masking=True):
    """Represents a websocket stream of bytes flowing in and out.

    The stream doesn't know about the data provider itself and
    doesn't even know about sockets. Instead the stream simply
    yields for more bytes whenever it requires them. The stream owner
    is responsible to provide the stream with those bytes until
    a frame can be interpreted.

    .. code-block:: python
       :linenos:

       >>> s = Stream()
       >>> s.parser.send(BYTES)
       >>> s.has_messages
       False
       >>> s.parser.send(MORE_BYTES)
       >>> s.has_messages
       True
       >>> s.message
       <TextMessage ... >

    Set ``always_mask`` to mask all frames built.

    Set ``expect_masking`` to indicate masking will be
    checked on all parsed frames.
    """

    self.message = None
    """
        Parsed test or binary messages. Whenever the parser
        reads more bytes from a fragment message, those bytes
        are appended to the most recent message.
        """

    self.pings = []
    """
        Parsed ping control messages. They are instances of
        :class:`ws4py.messaging.PingControlMessage`
        """

    self.pongs = []
    """
        Parsed pong control messages. They are instances of
        :class:`ws4py.messaging.PongControlMessage`
        """

    self.closing = None
    """
        Parsed close control messsage. Instance of
        :class:`ws4py.messaging.CloseControlMessage`
        """

    self.errors = []
    """
        Detected errors while parsing. Instances of
        :class:`ws4py.messaging.CloseControlMessage`
        """

    self._parser = None
    """
        Parser in charge to process bytes it is fed with.
        """

    self.always_mask = always_mask
    self.expect_masking = expect_masking

  @property
  def parser(self):
    if self._parser is None:
      self._parser = self.receiver()
      # Python generators must be initialized once.
      next(self.parser)
    return self._parser

  def _cleanup(self):
    """
    Frees the stream's resources rendering it unusable.
    """
    self.message = None
    if self._parser is not None:
      if not self._parser.gi_running:
        self._parser.close()
      self._parser = None
    self.errors = None
    self.pings = None
    self.pongs = None
    self.closing = None

  def text_message(self, text):
    """
    Returns a :class:`ws4py.messaging.TextMessage` instance
    ready to be built. Convenience method so
    that the caller doesn't need to import the
    :class:`ws4py.messaging.TextMessage` class itself.
    """
    return TextMessage(text=text)

  def binary_message(self, bytes):
    """
    Returns a :class:`ws4py.messaging.BinaryMessage` instance
    ready to be built. Convenience method so
    that the caller doesn't need to import the
    :class:`ws4py.messaging.BinaryMessage` class itself.
    """
    return BinaryMessage(bytes)

  @property
  def has_message(self):
    """
    Checks if the stream has received any message
    which, if fragmented, is now completed.
    """
    if self.message is not None:
      return self.message.completed

    return False

  def close(self, code=1000, reason=""):
    """
    Returns a close control message built from
    a :class:`ws4py.messaging.CloseControlMessage` instance,
    using the given status ``code`` and ``reason`` message.
    """
    return CloseControlMessage(code=code, reason=reason)

  def ping(self, data=""):
    """
    Returns a ping control message built from
    a :class:`ws4py.messaging.PingControlMessage` instance.
    """
    return PingControlMessage(data).single(mask=self.always_mask)

  def pong(self, data=""):
    """
    Returns a ping control message built from
    a :class:`ws4py.messaging.PongControlMessage` instance.
    """
    return PongControlMessage(data).single(mask=self.always_mask)

  def receiver(self):
    """
    Parser that keeps trying to interpret bytes it is fed with as
    incoming frames part of a message.

    Control message are single frames only while data messages, like text
    and binary, may be fragmented accross frames.

    The way it works is by instanciating a :class:`wspy.framing.Frame` object,
    then running its parser generator which yields how much bytes
    it requires to performs its task. The stream parser yields this value
    to its caller and feeds the frame parser.

    When the frame parser raises :exc:`StopIteration`, the stream parser
    tries to make sense of the parsed frame. It dispatches the frame's bytes
    to the most appropriate message type based on the frame's opcode.

    Overall this makes the stream parser totally agonstic to
    the data provider.
    """
    utf8validator = Utf8Validator()
    running = True
    frame = None
    while running:
      frame = Frame()
      while 1:
        try:
          some_bytes = yield next(frame.parser)
          frame.parser.send(some_bytes)
        except GeneratorExit:
          running = False
          break
        except StopIteration:
          frame._cleanup()
          some_bytes = frame.body

          # Let's avoid unmasking when there is no payload
          if some_bytes:
            if frame.masking_key and self.expect_masking:
              some_bytes = frame.unmask(some_bytes)
            elif not frame.masking_key and self.expect_masking:
              msg = CloseControlMessage(
                code=1002, reason="Missing masking when expected"
              )
              self.errors.append(msg)
              break
            elif frame.masking_key and not self.expect_masking:
              msg = CloseControlMessage(code=1002, reason="Masked when not expected")
              self.errors.append(msg)
              break
            else:
              # If we reach this stage, it's because
              # the frame wasn't masked and we didn't expect
              # it anyway. Therefore, on py2k, the bytes
              # are actually a str object and can't be used
              # in the utf8 validator as we need integers
              # when we get each byte one by one.
              # Our only solution here is to convert our
              # string to a bytearray.
              some_bytes = bytearray(some_bytes)

          if frame.opcode == OPCODE_TEXT:
            if self.message and not self.message.completed:
              # We got a text frame before we completed the previous one
              msg = CloseControlMessage(
                code=1002, reason="Received a new message before completing previous"
              )
              self.errors.append(msg)
              break

            m = TextMessage(some_bytes)
            m.completed = frame.fin == 1
            self.message = m

            if some_bytes:
              is_valid, end_on_code_point, _, _ = utf8validator.validate(some_bytes)

              if not is_valid or (m.completed and not end_on_code_point):
                self.errors.append(
                  CloseControlMessage(code=1007, reason="Invalid UTF-8 bytes")
                )
                break

          elif frame.opcode == OPCODE_BINARY:
            if self.message and not self.message.completed:
              # We got a text frame before we completed the previous one
              msg = CloseControlMessage(
                code=1002, reason="Received a new message before completing previous"
              )
              self.errors.append(msg)
              break

            m = BinaryMessage(some_bytes)
            m.completed = frame.fin == 1
            self.message = m

          elif frame.opcode == OPCODE_CONTINUATION:
            m = self.message
            if m is None:
              self.errors.append(
                CloseControlMessage(code=1002, reason="Message not started yet")
              )
              break

            m.extend(some_bytes)
            m.completed = frame.fin == 1
            if m.opcode == OPCODE_TEXT:
              if some_bytes:
                is_valid, end_on_code_point, _, _ = utf8validator.validate(some_bytes)

                if not is_valid or (m.completed and not end_on_code_point):
                  self.errors.append(
                    CloseControlMessage(code=1007, reason="Invalid UTF-8 bytes")
                  )
                  break

          elif frame.opcode == OPCODE_CLOSE:
            code = 1005
            reason = ""
            if frame.payload_length == 0:
              self.closing = CloseControlMessage(code=1005)
            elif frame.payload_length == 1:
              self.closing = CloseControlMessage(
                code=1005, reason="Payload has invalid length"
              )
            else:
              try:
                # at this stage, some_bytes have been unmasked
                # so actually are held in a bytearray
                code = int(unpack("!H", bytes(some_bytes[0:2]))[0])
              except struct.error:
                reason = "Failed at decoding closing code"
              else:
                # Those codes are reserved or plainly forbidden
                if code not in VALID_CLOSING_CODES and not (2999 < code < 5000):
                  reason = "Invalid Closing Frame Code: %d" % code
                  code = 1005
                elif frame.payload_length > 1:
                  reason = some_bytes[2:] if frame.masking_key else frame.body[2:]

                  if not py3k:
                    reason = bytearray(reason)
                  is_valid, end_on_code_point, _, _ = utf8validator.validate(reason)
                  if not is_valid or not end_on_code_point:
                    self.errors.append(
                      CloseControlMessage(code=1007, reason="Invalid UTF-8 bytes")
                    )
                    break
                  reason = bytes(reason)
              self.closing = CloseControlMessage(code=code, reason=reason)

          elif frame.opcode == OPCODE_PING:
            self.pings.append(PingControlMessage(some_bytes))

          elif frame.opcode == OPCODE_PONG:
            self.pongs.append(PongControlMessage(some_bytes))

          else:
            self.errors.append(CloseControlMessage(code=1003))

          break

        except ProtocolException:
          self.errors.append(CloseControlMessage(code=1002))
          break
        except FrameTooLargeException:
          self.errors.append(
            CloseControlMessage(code=1002, reason="Frame was too large")
          )
          break

      frame._cleanup()
      frame.body = None
      frame = None

      if self.message is not None and self.message.completed:
        utf8validator.reset()

    utf8validator.reset()
    utf8validator = None

    self._cleanup()
